Chemistry » Quantitative Aspects of Chemical Change » Volume Relationships In Gaseous Reactions

# Summary and Main Ideas

## Summary

• The volume of one mole of gas at STP is $$\text{22.4}$$ $$\text{dm^{3}}$$

• For any number of moles of gas at STP we can use $$V_{g} = \text{22.4}n_{g}$$ to find the volume.

• The volume relationship for two gases in a reaction is given by: $$V_{A} = \frac{a}{b}V_{B}$$.

where $$V_{A}$$ is the volume of gas A, $$V_{B}$$ is the gas B, $$a$$ is the stoichiometric coefficient of gas A and $$b$$ is the stoichiometric coefficient of gas B.

• The concentration of a solution can be calculated using: $$C = \frac{n}{V}$$

where C is the concentration (in $$\text{mol·dm^{3}}$$), n is the number of moles of solute dissolved in the solution and V is the volume of the solution (in $$\text{dm^{3}}$$).

• A standard solution is a solution in which the concentration is known to a high degree of precision. For the purposes of calculations, a standard solution can be thought of as one in which the concentration is a set value.

• A titration is a technique for determining the concentration of an unknown solution. We can calculate the unknown concentration using:

\begin{align*} \frac{C_{A}V_{A}}{a} &= \frac{C_{B}V_{B}}{b} \end{align*}

• A limiting reagent is a reagent that is completely used up in a chemical reaction.

• An excess reagent is a reagent that is not completely used up in a chemical reaction.

• Percent yield is calculated using:

$\% \text{yield} = \frac{\text{actual yield}}{\text{theoretical yield}} \times \text{100}$

Where the actual yield is the amount of product that is produced when you carry out the reaction and the theoretical yield is the amount of product that you calculate for the reaction using stoichiometric methods.

• The empirical formula is the simplest formula of a compound.

• The molecular formula is the full formula of a compound.

• Percent purity is calculated using:

$\% \text{purity} = \frac{\text{mass of compound}}{\text{mass of sample}} \times \text{100}$

 Physical Quantities Quantity Unit name Unit symbol Concentration ($$C$$) moles per cubic decimetre $$\text{mol·dm^{-3}}$$ Mass ($$m$$) kilogram $$\text{kg}$$ Moles ($$n$$) moles $$\text{mol}$$ Volume ($$V$$) meters cubed $$\text{m^{3}}$$

Table: Units used in quantitative aspects of chemical change